Filtration systems are used for treatment of water and wastewater for removal of suspended and/or dissolved impurities.
The filtration systems are usually one-stage, gravity or pressure flow systems. Filters can operate in a horizontal or vertical flow pattern: however, the vertical flow pattern is predominant. In the vertical flow pattern the liquid flow through the filter can be downward or upward during the production cycle and the filter backwashing is usually with upward liquid flow, however a combination of upward and downward liquid flow is also possible. Single or multiple filters can be used and multiple filters can be operated in series or in parallel arrangements. Filters can use filtration media with specific gravity higher or lower than the specific gravity of the liquid filtered.
The gravity flow filtration systems depend on a static water pressure (head) above the filter media for the water to flow through the media. The available static water pressure above the filter media is directly proportional to the filter vessel height above the filter media. Therefore, the higher the filter vessel above the filter media the longer the operating cycle is expected for the same water quality and flow rate treated.
The filtration systems are usually provided for removal of suspended solids or dissolved impurities and each usually requires an independent filtration apparatus.
If two stage suspended and/or dissolved solids filtration system is required, two independent filtration apparatus, operating in series are used.
Similarly, if suspended solids filtration and dissolved impurities filtration processes are required two independent filtration apparatus, operating in series are used.
Filter media need to be backwashed and preferably rinsed after they are plugged with the impurities which they remove. Each filtration apparatus is backwashed and preferably rinsed independently. The backwash and rinse water is predominantly wasted. The rinse water is predominantly the same as the backwash water and the rinse cycle follows the backwash cycle, although, the backwash water flow rate can be different or the same as the rinse water flow rate.
The invention offers several advantages over the conventional filtration systems as follows:                The novel syphon piping and control system, used in this invention, allows for reduction of the filter headroom requirements and it extends the filter operating cycle between the filter backwashings.        The novel syphon piping and control system design prevents the filter media from being exposed and disturbed on the surface during the filtration process.        The novel piping and control system design uses simple open/close automatic control valves to control the water level above the filter media and to perform the production, backwashing and rinsing processes, and minimizes the number of the control valves needed to perform all the processes.        The two-stage filtration system in one vertical apparatus reduces the foot print requirements and permits use of the same or different filtration media in each stage of the filtration apparatus.        The two-stage filtration system permits independent and simultaneous backwashing and rinsing of the filter media in both stages of the filtration system which reduces the backwash water and time requirements.        The two-stage filtration system in one apparatus requires less extensive controls and reduces the costs of the treatment system.        